Abrasive particulate is particulate matter having aerodynamic diameters larger than approximately 20 micrometers. The abrasiveness of the particulate matter increases with the square of the particle diameter and proportional to the particle density and particle hardness. Particles in the range of 0.01 to more than 500 micrometers (aerodynamic) are released as fugitive emissions from a variety of process sources such as belt conveyors, bucket elevators, vibrating screens, and crushers. Although the fugitive dust is caught by a ventilation system hood, the abrasive particulate matter damages the equipment in the ventilation system by scouring the interior surfaces during transport through elbows, branch junctions, and other areas where the air stream is forced to change direction. Large particulate matter is encountered in industries in a variety of mineral processing sources such as crushed stone plants, sand and gravel processing facilities, roofing granule production facilities, Portland cement plants, and some glass manufacturing and wood products industry sources where solids have been cut, screened, transported, or crushed.
Common ventilation systems in place to protect workers in accordance with OSHA and MSHA exposure standards include hood enclosures over process equipment that are ducted to ventilation systems and eventually to particulate matter control systems for the removal of the particulate matter before release of the air stream to the environment. However, the air handling ductwork in these ventilation systems can be damaged by the abrasive particles. The abrasive dust creates holes in the ductwork which can decrease the effectiveness of the hoods and allow fugitive dust to remain entrained or become re-entrained in the plant environment near the process equipment. Depending on the material, abrasive particulate can damage ductwork to such an extent that some industries patch their systems on a regular basis and in severe cases require frequent, highly expensive duct replacement.
Ventilation system ducts constructed of abrasion-resistant steels and of abrasion-resistant duct lining have been found to be costly and short-term solutions. It is preferable to remove the damaging large particles prior to their entry to, and transport in the ventilation system ducts.
The separation of large particles prior to entry into the ventilation system is preferably done in a way that does not impose a large static pressure drop on the ventilation system. Alternative systems such as cyclones used as preseparators impose static pressure drops of 2 to 5 inches of water column, and most ventilation systems are not capable of handling this flow resistance without compromising other fugitive dust pick-up hoods in other parts of a large and complex ventilation system in the industrial facility. The particle separator disclosed here has a very low static pressure drop and can be easily retrofitted into most existing ventilation systems.